The present invention relates to apparatus for delayed completion of electric circuits, especially to improvements in apparatus for delayed firing of electronic flash units which can be used with still cameras or motion picture cameras to furnish artificial light during the making of exposures.
Cameras which are intended for use with electronic flash units normally contain a synchronizing switch which is closed in response to actuation of camera release so that the flash unit is fired with a certain delay which is necessary to insure that the subject or scene is properly illuminated at the exact moment when the shutter is open to admit scene light to the foremost unexposed film frame. However, certain cameras do not embody a synchronizing switch so that they cannot be used with electronic flash units. On the other hand, certain cameras, especially still cameras, embody indexible sockets for multiple flash lamp holders (e.g., those known as flashcubes or magicubes), and such cameras are provided with impellers or analogous operating means serving to fire a flash lamp in a multiple flash lamp holder at the exact moment when the shutter is open.